Duration of Lactation and Incidence of the Metabolic Syndrome in Women of Reproductive Age According to Gestational Diabetes Mellitus Status: A 20-Year Prospective Study in CARDIA—The Coronary Artery Risk Development in Young Adults Study
Gunderson EP, Jacobs DR Jr, Chiang V, Lewis CE, Feng J, Quesenberry CP Jr, Sidney S.
Diabetes. 2009 Dec 3.
Objective(s): To prospectively assess the association between lactation duration and incidence of the metabolic syndrome (MetS) among women of reproductive age.
Research Design and Methods: Participants were 1,399 women (39% black, aged 18–30) in the Coronary Artery Risk Development in Young Adults (CARDIA) Study, an ongoing multi-center, population-based, prospective observational cohort study conducted in the United States. Women were nulliparous and free of the MetS at baseline (1985–86) and before subsequent pregnancies, and re-examined 7, 10, 15 and/or 20 years after baseline. Incident MetS cases were identified according to NCEP ATP III criteria. Complementary log-log models estimated relative hazards of incident MetS among time-dependent lactation duration categories by gestational diabetes mellitus (GDM) adjusted for age, race, study center, baseline covariates (BMI, MetS components, education, smoking, physical activity) and time-dependent parity.
Results: Among 704 parous women (620 non-GDM, 84 GDM), there were 120 incident MetS cases in 9,993 person-years (overall incidence rate 12.0 per 1,000 person-years;10.8 for non-GDM, 22.1 for GDM). Increasing lactation duration was associated with lower crude MetS incidence rates from 0–1 month through >9 months (p<0.001). Fully adjusted relative hazards showed that risk reductions associated with longer lactation were stronger among GDM (RHs range:0.14 to 0.56;p=0.03) than non-GDM groups(RHs range:0.44 to 0.61;p=0.03).
Conclusions: Longer duration of lactation was associated with lower incidence of the metabolic syndrome years post-weaning among women with a history of GDM and without GDM controlling for preconception measurements, BMI, socio-demographic and lifestyle traits. Lactation may have persistent favorable effects on women’s cardiometabolic health.